Harvard researchers have linked to strict FDA approval deadlines, providing statistical evidence to back up what critics have been saying for years — that the rush to approve new drugs often means the FDA overlooks the dangers.

The study, published in the New England Journal of Medicine, says that since 1993, 97 drugs have been approved in the two-month window, and 14% of them have gone on to show serious safety problems, compared with 3% for 216 other drugs approved during that time.

“PDUFA deadlines have appreciably changed the approval decisions of the FDA. Once medications are in clinical use, the discovery of safety problems is more likely for drugs approved immediately before a deadline than for those approved at other times,” the study concluded.